“Depths of utilities can be assumed.”
Locator depths are estimations, because the surface grade often changes since the time that the utilities were originally installed. Many times utilities are installed before excavation, fill and development happen that can change the surface grade dramatically. The depth of utilities can never be assumed. Even small portions of utility lines that are as small as a city block can dip or rise in depth. It is important that utilities are exposed to verify their exact location and depth.
“It will never happen to me mentality.”
It is easy to think a utility strike will not happen to you, because you have never had a disastrous strike before, but utility strikes happen every day and it is important to never skip safety measures. Cutting corners, rushing to get the job done, getting lazy or complacent on the job, can all lead to major consequences.
“Exposing to the depth of the utility is good enough.”
Only exposing the depth of existing utilities is not proper practice and may violate OSHA regulations. Along with exposing the depth of utilities, you must also verify that no utilities are hiding underneath and always expose to the depth of the intended bore path. Visually observe the drill head as it passes the utility, and again during each pass of the reamer. The reamer can shift in the bore during pullback and strike a utility that appeared to have plenty of clearance.
“Just drill deeper to avoid existing utilities.”
Drilling deep creates problems such as locating and exposing for current and future excavation. At approximately 10’, locators become less accurate with locating the underground infrastructure. If the existing utility goes undetected, an underground strike can occur. Also, best practices dictate that the existing utility being crossed be exposed to the depth of the intended bore. That is difficult for deeper bores and if the line at that depth is ever damaged, the utility will have to dig deeper requiring a longer response time and greater expense.
“Sewer lines don’t need to be or cannot be located.”
If a sewer line is damaged during the installation of a utility, the sewer will eventually clog because of the intersection of the newly installed utility. To relieve the clog, a plumber will run a snake into the sewer and can damage the intersecting line. If it is an electric line, the plumber could be electrocuted. If it is a gas line, the gas can migrate into the sewer and ignite once inside homes or businesses.
“No locate marks = no utilities.”
If there are no marks, this could mean that it was not yet located. Many states have a positive response system so that it can be verified that all utilities have cleared the area.
On-site, privately installed lines may not be recorded by the utility companies or located by the locating service. Inspect the area for evidence of underground activity, disturbed and repaired soil or pavement, utility boxes, conduit coming out of the ground, etc.
“My responsibility for damage prevention ends when I call 811. If something happens, 811 is liable.”
811 does not locate utilities. They coordinate with the utilities and their contracted locating services to have the area located. It is the responsibility of the excavator to verify that locates have been completed and are accurate. This includes contacting utilities that don’t subscribe to 811, looking in the area for signs of utilities (outbuildings, pipeline markers, light poles, utility boxes, meters, etc.) and exposing the utilities to verify the locates. If an excavator damages a line, there are always costs to bear and effects on reputation.
“Exposing utilities (potholing) is included as part of the contract price for the drilling.”
This shouldn’t be assumed. To ensure potholing activity is included and is not shorted, it is recommended to separate this activity from the drilling in the quote. The project owner and contractor should work together to emphasize this as an important and integral part of the job.
“We have to accept whatever the caller gives us.”
When a contractor calls the Call Center or Utility, both parties have to be explicit and detailed with the information provided so an accurate and safe locates can be made.
“Electric strike alert systems can predict an electric strike.”
In some cases, the system may activate in the proximity of an energized line, but it cannot be relied upon to detect the line before a strike happens. If the electric strike system activates, always assume an electric strike has occurred.
Some strike systems detect a strike using only voltage detection via a voltage limiter. The voltage limiter is located away from the machine on a ground stake and detects the voltage difference between the ground stake and the drilling machine.
Other strike systems use both voltage and current detection. In addition to a voltage limiter, a current coil detects current flowing through the drill string. The system will only activate the alarm when voltage, current, or a combination of both voltage and current is above threshold limits.
For either system, if the alarm sounds, assume a strike has occurred.
Other strike systems use both voltage and current detection. In addition to a voltage limiter, a current coil detects current flowing through the drill string. The system will only activate the alarm when voltage, current, or a combination of both voltage and current is above threshold limits.
For either system, if the alarm sounds, assume a strike has occurred.
For the original article and more information, visit ICUEE.
